Generating unit with engine speed control device

ABSTRACT

The invention relates to a generating unit driven by a combustion engine. Control of the engine speed is carried out in a known manner via a mechanical control device which controls a throttle valve in the carburetor system of the engine. In case of a failure of the mechanical control device and, consequently, in case of a change in the engine speed outside a predetermined range, an electronic control system takes over to activate a firing element of the engine and control the engine speed, independently from the mechanical control system, in such a way that the engine speed is maintained within the predetermined range.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention pertains to a power-generating system.

2. Description of the Related Art

Mobile power-generating systems or producers usually consist of agenerator that is driven by an internal combustion engine. Commonly usedas the generator are synchronous or asynchronous generators whose outputvoltage at the generator depends on the rotor RPM, i.e. on the engineRPM. If the engine RPM's increase, the output voltage also increases,which in worst cases can lead to the destruction of the users connectedto the power producer.

To this end, internal combustion engines of known power-generatingsystems have a mechanical control system that maintains the engine RPMat a predetermined value within its operating range. It is possible forthe control action to be affected in such a way that the engine RPM canno longer be kept within the prescribed range, especially when themechanical controller is disrupted, for example by control rods beingblocked, broken springs, seized bearings or similar causes.

For expensive, technically complicated power generators—such as areknown from DE 196 38 357 A1, for example—another voltage control systemis connected in series in addition to the RPM control system, and thisadditional voltage control system monitors the voltage produced by thegenerator and changes it by a suitable control means, such as through arotor field control system or by changing the excitation. However, thevoltage control system has no effect on the engine RPM. As a result,although the voltage can be held at a preset value, the generatorvoltage frequency continues to depend on the engine RPM.

DE 43 11 670 A1 describes a known circuit arrangement for a voltagecontroller located at a generator output with which the field currentkeying ratio can be detected at the generator. If the field currentkeying ratio is at a high level, i.e. if there is a large power draw bythe users connected to the generator, this information can be detecteddirectly by the circuit and processed, resulting in the RPM of aninternal combustion engine that drives the generator being raisedsomewhat in order to satisfy the higher power draw at the generator.

From EP-A-0 352 759, a system to control actuating devices of anautomobile is known having a safety concept characterized by themonitoring of equal elements of the individual functional chains as wellas by the initiation of emergency measures if an error in one of theelements is detected during monitoring. The desired emergency measure isto either retain the current functional state or to change it in adirection that increases the safety level.

OBJECTS AND SUMMARY OF THE INVENTION

The objective of this invention is to provide a power-generating systemthat can prevent the above problems with respect to excess voltageincreases at increased engine RPM and with respect to increased voltagefrequency.

A power-generating system according to the invention an internalcombustion engine, a generator driven by the internal combustion engine,a mechanical control unit to control a RPM of the internal combustionengine, a RPM-determining unit, and an electronic control unit coupledto the RPM-determining unit to control the RPM of the internalcombustion engine, wherein the electronic control unit only controls theRPM, thus overriding an effect of the mechanical control unit, when theRPM-determining unit detects a RPM outside of a prescribed operatingrange.

According to the invention, an electronic RPM control system issuperimposed or connected in series to the known mechanical engine RPMcontrol system. If, due to a disruption of the mechanical controller,the engine RPM leaves the preset control range of the mechanicalcontroller, in particular if it exceeds it, the electronic controllerthat was inactive up until then activates and influences the RPM of theengine—preferably by means of its ignition. Influencing the ignition canbe done by interrupting it or by leaving out individual sparks. Also,the ignition timing can be changed.

BRIEF DESCRIPTION OF THE DRAWINGS

Due to the effect of the electronic RPM control system connected inseries, the RPM of the engine and thus of the generator stays within theprescribed RPM range. The output voltage at the generator also lieswithin the prescribed range accordingly with regard to its voltage leveland frequency.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The electronic control system makes it possible to correct any erroneousbehavior of the mechanical controller, which is an otherwise good way tocontrol the engine with regard to its use and emissions.

It is especially advantageous if a display is provided to deliver anoptical or acoustic signal, this display being activated when theelectronic control unit is controlling the RPM.

This and other advantages and features of the invention are explained inmore detail below with the help of a single FIGURE. What is shown is

FIG. 1 a schematic of a power-generating system according to theinvention.

In a power-generating system according to the invention to produce avoltage of prescribed level and frequency, an internal combustion engine1 is coupled mechanically to a generator 2 in a known fashion.

To regulate the RPM of the engine, a likewise known mechanicalcontroller 3 is provided that influences the position of a throttleplate 4 in the carburetor of the engine 1. Suitable as the mechanicalcontroller 3 are, for example, a wind vane, anemometer-type controller,a static plate, baffle plate controller or ball controller.

By means of the mechanical controller 3, it is possible to hold theengine RPM continuously in a prescribe RPM range, which leads to thedesired voltage with the prescribed frequency due to a predefined designof the generator 2.

However, the mechanical controller 3 is sensitive to mechanical andcorrosive influences. Thus, for example, broken springs, bent controlrods or seized bearings in the mechanics of the controller 3 can hinderthe RPM control function in such a way that the engine RPM increases orlowers in an undesired manner. In particular, the increase of the engineRPM leads to an increase in the output voltage for asynchronous orsynchronous machines used as the generator 2, which can result in adisruption of a user connected to the generator 2, not shown.

For this reason, an RPM-determining device 5 is provided, according tothe invention, which determines the RPM of the engine or generator shaftand conveys this information to an electronic control system 6. Suitableas RPM-determining devices 5 are common parts that, for example,determine the engine RPM through mechanical or optical means.

The electronic control system 6 tests whether the engine RPM is insideor outside of a prescribed operating range, which can be saved in theelectronic control system 6, for example. As long as the RPM is withinthe operating range, the electronic control unit 6 remains inactive.Otherwise, it directly influences an ignition unit 7 of the engine 1. Bychanging or deleting ignition times, it is possible for the controlsystem 6 to thus influence the engine RPM independent of the mechanicalcontroller 3. In the process, in particular, the rotation of the engine1 is prevented from going too fast such that the user connected to thegenerator 2 is effectively protected against over-voltage or a voltagewith too high of a frequency.

Of course, the RPM influence can be accomplished by the electroniccontroller 6 in other ways in other embodiments of the invention.

The electronic controller 6 and the RPM-determining unit 3 can be addedin a simple manner to pre-existing power-generating systems withouthaving to change the technical concept of the systems. In the process,the electronic controller 6 can be constructed in a manner that iscommonly known to the expert.

In particular, complicated and expensive control systems in thegenerator portion, for example to influence the magnetic excitation, canbe prevented.

Preferably, an acoustic or optic display is provided that is turned onby the electronic controller 6 and indicates that the electroniccontroller 6 is active, which is equivalent to mean that the engine RPMwas determined to be outside of the prescribed range due to a disruptionin the mechanical controller 3.

In the electronic controller 6, a timing circuit can also be providedwhich allows the electronic controller 6 to engage only after a certaintime has elapsed after the determination that the RPM has gone too high.

I claim:
 1. A power-generating system comprising: a. an internal combustion engine; b. an electric generator that is driven by the internal combustion engine; c. a mechanical control unit that is configured to control a RPM of the internal combustion engine; d. a RPM-determining unit that is configured to determine the RPM of the internal combustion engine; and e. an electronic control unit that is coupled to the RPM-determining unit and that is configured to control the RPM of the internal combustion engine, wherein the electronic control unit only controls the RPM of the internal combustion engine, thus overriding operation of the mechanical control unit, when the RPM-determining unit determines that the internal combustion engine's RPM outside of a prescribed operating range.
 2. A power-generating system according to claim 1, wherein the electronic control unit controls a control unit of the internal combustion engine.
 3. A power-generating system according to claim 1, wherein a display delivers an optical or acoustic signal if the electronic control unit is controlling the RPM.
 4. A power-generating system according to claim 2, further comprising a display that provides an optical or acoustic indication that the electronic control unit is controlling the internal combustion engine's RPM.
 5. A power-generating system according to claim 1, further comprising a timing circuit that allows the electronic controller to engage only after a prescribed time has elapsed after the RPM-determining unit detects an internal combustion engine RPM above the prescribed operating range.
 6. A power-generating system according to claim 1, wherein the mechanical controller comprises at least one of a wind vane, an anemometer-type controller, a static plate controller, a baffle plate controller, and a ball controller.
 7. A power-generating system according to claim 2, wherein the control unit of the internal combustion engine comprises an ignition unit.
 8. A power-generating system comprising: a. an internal combustion engine; b. an electric generator that is driven by the internal combustion engine to generate electric power; c. a mechanical control unit that is configured to control a rotational velocity of the internal combustion engine; d. a rotational velocity sensor that is configured to determine the rotational velocity of the internal combustion engine; and e. an electronic control unit that is coupled to the rotational velocity sensor and to the internal combustion engine, wherein the electronic control unit is operable, when the internal combustion engines rotational velocity as detected by the rotational velocity sensor is outside of a prescribed operating range, to override operation of the mechanical control unit and control the rotational velocity of the internal combustion engine.
 9. A power-generating system according to claim 8, wherein the electronic control unit controls a control unit of the internal combustion engine.
 10. A power-generating system according to claim 8, further comprising a display that delivers an optical or acoustic signal if the electronic control unit is controlling the rotational velocity of the internal combustion engine.
 11. A power-generating system according to claim 9, further comprising a display that provides an optical or acoustic indication that the electronic control unit is controlling the rotational velocity of the internal combustion engine.
 12. A power-generating system according to claim 8, further comprising a timing circuit that allows the electronic controller to engage only after a prescribed time has elapsed after the internal combustion engines rotational velocity is detected as being above the prescribed operating range.
 13. A power-generating system according to claim 8, wherein the mechanical controller comprises at least one of a wind vane, an anemometer-type controller, a static plate controller, a baffle plate controller, and a ball controller.
 14. A power-generating system according to claim 2, wherein the control unit of the internal combustion engine comprises an ignition control unit. 